In general, power devices using compound semiconductor elements such as GaAs, GaN are required to achieve a higher frequency. As a result, a current density increases, which generates heat, and therefore, the operation temperature of the device increases.
As the temperature during operation of the device increases, characteristics are usually deteriorated, e.g., an ON-resistance and a leakage current increase. Therefore, heat dissipating performance of a device is a parameter controlling the characteristics of the device.
Therefore, in order to suppress the degradation of the device characteristics, a method for dissipating the heat generated in the semiconductor element is used. The method includes replacing a supporting substrate with a material having high heat dissipating performance or providing a radiation fin in a package. However, since the heat is dissipated via the semiconductor substrate having a relatively low thermal conductivity and further via the package, the thermal path becomes longer, which makes it difficult to obtain sufficient heat dissipation effect.